Streeeeetching the Range

[zazaboeing]

There are things only FS encourage us doing, and one to mention is the below described test. I would doubtedly do this in real life for several reasons, including low fuel arrival, imprecise fuel gages, and seating for almost 11 hours wearing an oxygen cannula is NO FUN. Consider this being done in a delivery flight, or a ferry one with no ferry tanks over somewhere you couldn't get fuel. I did this at home, with nice air conditioning, sleeping in between, accessing facebook, watching TV, going to the supermarket etc while making use of the so useful Away of Keyboard feature. A 7 hours flight in a "roomy" 737 where you have food, toilet and can stand is already too boring, imagine this being done in a piston single.

So, just out of curiosity I was out for a test regarding specific fuel consumption, getting the maximum range for the Comanche and the 182 @ high altitudes on a ferry flight configuration (133 Kgs of total payload - this includes Pilot, baggage and portable oxygen system) with full tanks.

Route was from Recife (SBRF) to Curitiba (SBBI) - 1360nm!! The usual choice here, of course, would be to make a stopover and completing the flight with even shorter time due to more powerful cruise settings. But, let's just assume I couldn't for some reason.
Turned off weather, and all was ISA, zero wind.

Comanche direct climb to FL 200.
C182 direct climb to FL180.

Reaching the Cruise levels was painful as you might guess, a little easier (and slower) with the 182 due to its better autopilot control.

First hours of cruise required some higher RPM to maintain an acceptable cruise speed, managing the thin line between adding too much power and reducing to a point your specific fuel consumption would rise again due to increased drag in very slow IAS. I kept something around Best Glide Speed which would produce the minimum amount of drag. Higher speed with higher weights and lowering as fuel was consumed.

After 1/3 of flight time completed, I reduced to the minimum cruise setting possible, full throttle on both planes (of course!), minimum RPM and operating at LOP in the Comanche and @ Peak EGT in the 182. Speeds were terrible, as this is not the main purpose of a flight like this (something around 124 KTAS on the Piper, and 119 on the C182).

The Comanche did a pretty decent job getting the flight done in something around 10:10 giving me around 11 hours of endurance! A 1400nm range plus a NEARBY alternate!
The 182 had fuel low lights on during mid descent and landed after 10:50 of flight with 33 liters remaining upon landing. Not much room to spare.

Below, there's a ps of the Comanche at FL200 just prior to start descent, 19.1nm/gl!!, just sipping fuel in a rate a motorcycle would do.



And here, the C182, in short final, after 10:49 of flight.



Oxygen "magic supply" used as per http://a2asimulations.com/forum/viewtop ... lit=oxygen

[n421nj]

Im conflicted. I get why you turned off the weather and great experiment but part of me says leave the weather on and see how things pan out.

[zazaboeing]

Im conflicted. I get why you turned off the weather and great experiment but part of me says leave the weather on and see how things pan out.

Yeah, but the idea was not to simulate a real flight, but to see how things turns out without environmental influence. The wind at those levels would be a great helper or killer.

[Nick - A2A]

Interesting experiment Rafael - thanks for posting. I'm happy to see someone finding the 'magic oxygen supply' helpful. When testing it, I seem to recall that I took the Comanche up to FL200 as well, and found the climb didn't take quite as long as I'd feared. The performance and climb rate (what was left of it) at that altitude seemed pretty convincing to me, though I didn't try for any endurance records.

Cheers,
Nick

P.S. English is a strange language. Though "undoubtedly" is a word, "doubtedly" isn't. Instead: "It's doubtful I'd do this in real life..." (Sorry for the unsolicited tip!)

[William Hughes]

Book says you can get to 22,000 feet with the engine. I'll bet the last 4,000 feet is flying on the edge of a stall the entire time - any tiny disturbance and she'd drop a wing.

[zazaboeing]

Book says you can get to 22,000 feet with the engine. I'll bet the last 4,000 feet is flying on the edge of a stall the entire time - any tiny disturbance and she'd drop a wing.

The magic is to never let it drop below 80 kts by increasing RPM to 2400 and enriching a little during the climb, vsi as low as 100ft/m will do the job.

Also, 22000 will require an oxygen mask I guess, the cannula is not enough.